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1. Buy something something else, but that's advertised as Bitcoin. There are plenty of "Bitcoin whatever" altcoins, but they use different blockchains.
I wouldn't doubt people who have used bitcoin for years, but what if:
If bitcoin had been legalized worldwide but with policies like Elsalvador (under control), then not everyone could not identify real and fake bitcoins because they were not introduced to how to transact bitcoin onchain. In fact bitcoin addresses can accept some bitcoin forks. If one day a scammer builds a phishing tx explorer site and designs the interface as if it belonged to real bitcoin's blockchain, the victims are unaware because of their ignorance.
Perhaps the OP's question is irrefutable for some reason. And what makes me believe that bitcoin can be "counterfeited" is that there are cases of wrong deposits on CEX, which BCH they thought was BTC.
El Salvador situation is indeed different - they use LN there on a specific software. But that software will work with bitcoin nodes. I don't think it works with anything else. But yes, the user should get used with the tool.
And, as help, their govt has sent them some free money. Receiving them it's a good indicator for using the right tool in the right way.
But you do have a good point about multi-coin block explorers and wallets, but if the user has a good - proper - wallet, that will work on bitcoin blockchain and he will see that something is wrong with whatever the scammer shows.
And multi-blockchain wallet and explorers should tell the
full name of the coin for which they show the transactions. One has to open his eyes, though...
Plus, if anything is fishy, if anything is different than expected, one can come here and ask with clear data at hand.